Worldwide air traffic is projected to double every ten to fourteen years and the International Civil Aviation Organization (ICAO) forecasts world air travel growth of five percent per annum until the year 2020. Such growth may have an influence on flight performance and may increase the workload of the flight crew. In order to handle the expected increase in air traffic, the Next Generation Air Transportation System (NextGen) will introduce major transformations in Air Traffic Management (ATM), for example, aircraft trajectory-based operations. Trajectory-based operations will manage National Airspace System (NAS) resources by requiring aircraft to precisely follow custom-made 4-D trajectories consisting of a specified path along-path time conformance requirements. This promotes prescribing and accurately following trajectories that ensure separation and optimize traffic flow management over different time horizons, which will significantly improve flight safety and performance.
However, one issue associated with the 4D operational concept is that deconfliction of the airspace and prevention of a separation infringement requires a reliable 4D trajectory. It uses Required Time of Arrival (RTA) to guarantee the reliability of time of arrival at a merging waypoint (RTA waypoint). However, the reliability before the waypoint is not guaranteed. An aircraft not compliant with its 4D trajectory may allow the spacing between aircraft to become too small.
Known flight management system (FMS) software is able to handle only AT or BELOW speed restrictions for climbs and descents. And from the RTA perspective, a recently developed system (Honeywell U.S. Pat. No. 8,406,939) accounts for a speed pad on top of the descent speed restriction, in order to protect the speed from premature saturation in the restriction area. The addition of the AT OR ABOVE and AT speed constraints raises the issue of how to handle them together with the RTA and maintain reliability of the RTA. With these supplementary types of speed restrictions, a new mechanism is needed to determine the speeds required along the flight trajectory to satisfy the RTA, and a new speed pad is needed that can be later used in the constrained area. The AT or ABOVE speed constraint definition is slightly different from the intuitive expectation wherein the speed in descent is expected to be above the constraint value before the constrained waypoint, and vice versa for climb. The AT speed constraint is a combination of AT or ABOVE and AT or BELOW components. When an AT speed constraint is defined in the flight plan, either in climb or descent, the whole flight phase undesirably may be considered under speed restrictions, which is detrimental to achieving a time constraint.
Accordingly, it is desirable to provide a system and method for managing time error at a RTA waypoint in the presence of an AT speed constraint or an AT or ABOVE speed constraint. Furthermore, other desirable features and characteristics of the exemplary embodiments will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.